Subsets of glioblastoma multiforme defined by molecular genetic analysis

Loss of chromosome 10 in glioblastoma: relation to proliferation and angiogenesis

Loss of chromosome 10 was assessed in 17 specimens of glioblastoma (GBM) by fluorescence in situ hybridization (FISH) technique using the centromere probe for chromosome 10. Cytospinned smear specimens were prepared from paraffin-embedded specimens. The percentage of nuclei containing a single fluorescent signal ranged from 19.2 to 88. 0% (mean, 49.3%). Thirteen tumors (76.5%) were designated as monosomy 10 because the proportion of single-signal nuclei exceeded the cut-off value (31.5%: mean of five control materials +3 standard deviations). The results confirmed the importance of the loss of chromosome 10 for the development of GBM, although no significant correlation was demonstrated between the loss of chromosome 10 and survival. In addition, proliferation potential and angiogenesis of GBM were immunohistochemically analyzed using antibodies against Ki-67 antigen (MIB-1), factor VIII-related antigen (FVIII R/Ag) and vascular endothelial growth factor (VEGF), respectively. The labeling indices of MIB-1 (1.5-57.8%) and the number of blood vessels immunoreactive for FVIII R/Ag (18-279/10 high-power fields) were not significantly related to the loss of chromosome 10. Vascular endothelial growth factor immunoreactivity in areas microvessels were counted was seen in 12 cases. However, neither the loss of chromosome 10 nor number of vessels was not correlated with VEGF expression. Other genetic abnormalities as well as loss of chromosome 10 may be involved in the cell proliferation and angiogenesis of GBM.

Prognostic value of tumour associated antigen immunoreactivity and apoptosis in cerebral glioblastomas: an analysis of 168 cases

AIMS

To evaluate a possible association between clinical outcome in patients with glioblastoma and expression of some immunohistochemical variables and apoptosis.

METHODS

168 selected patients with cerebral glioblastomas were studied retrospectively. Tumour specimens were examined immunohistochemically with antibodies to proliferating cell nuclear antigen (PCNA), p53, bcl-2, and epidermal growth factor receptor (EGFR) to detect the intracellular receptor domain. Apoptosis was detected by in situ end labelling. Multivariate analysis was performed using the Cox proportional hazard model.

RESULTS

On univariate analysis the PCNA labelling index, immunoexpression of EGFR, and the apoptotic index were significantly related to glioblastoma outcome. Survival time was reduced as PCNA labelling index increased and apoptotic index decreased (p = 0.0073 and p = 0.00031, respectively). Survival time in patients with EGFR positive tumours was found to be reduced (p = 0.00024). Multivariate analysis showed independent prognostic value for the EGFR positivity and apoptotic index only (p = 0.0053 and p = 0.0039, respectively). There was no association between clinical outcome of glioblastoma and p53 or bcl-2 immunostaining.

CONCLUSIONS

EGFR immunoreactivity and apoptotic index were found to be useful for assessing prognosis of individual glioblastomas but it seems unlikely that p53 and bcl-2 immunohistochemistry will be of value in determining survival in such patients.

Cyclin D1 expression in astrocytomas is associated with cell proliferation activity and patient prognosis

An important positive regulator of the cell cycle, cyclin D1, is often amplified and overexpressed in malignancies. Cyclin D1 aberrations were analysed in grade II-IV astrocytomas by fluorescence in situ hybridization (FISH), mRNA in situ hybridization and immunohistochemistry. Proliferation activity was determined by Ki-67(MIB-1) immunolabelling and mitotic counting. High cyclin D1 expression was observed in grade IV astrocytomas (grades II-III versus grade IV; mRNA expression: p<0.001; immunoexpression: p=0.013), and correlated with poor patient survival (p<0.001, n=46). Upregulated cyclin D1 expression was also closely associated with poor patient prognosis in grade II-III astrocytomas (p<0.001, n=30). Cyclin D1 gene was not found to be amplified (n=7). Cell proliferation activity was significantly increased in tumours exhibiting high cyclin D1 mRNA levels (Ki-67(MIB-1): p<0.001; mitotic count: p<0.001) and high cyclin D1 protein expression (Ki-67(MIB-1): p=0.002; mitotic count: p=0.012). These results indicate that increased production of cyclin D1 is closely associated with high cell proliferation activity and aggressive behaviour in diffusely infiltrating astrocytomas.

Molecular genetic alterations in radiation-induced astrocytomas

Astrocytic tumors occasionally arise in the central nervous system following radiotherapy. It is not clear if these gliomas represent a unique molecular genetic subset. We identified nine cases in which an astrocytoma arose within ports of previous radiation therapy, with total doses ranging from 2400 to 5500 cGy. Irradiated primary lesions included craniopharyngioma, pituitary adenoma, Hodgkin's lymphoma, ependymoma, pineal neoplasm, rhabdomyosarcoma, and three cases of lymphoblastic malignancies. Patients ranged from 9 to 60 years of age and developed secondary tumors 5 to 23 years after radiotherapy. The 9 postradiation neoplasms presented as either anaplastic astrocytoma (3 cases) or glioblastoma multiforme (6 cases). Two of the latter contained malignant mesenchymal components. We performed DNA sequence analysis, differential polymerase chain reaction (PCR), and quantitative PCR on DNA from formalin-fixed, paraffin-embedded tumors to evaluate possible alterations of p53, PTEN, K-ras, EGFR, MTAP, and p16 (MTS1/CDKN2) genes. By quantitative PCR, we found EGFR gene amplification in 2 of 8 tumors. One of these demonstrated strong immunoreactivity for EGFR. Quantitative PCR showed chromosome 9p deletions including p16 tumor suppressor gene (2 of 7 tumors) and MTAP gene (3 of 7). Five of 9 tumors demonstrated diffuse nuclear immunoreactivity for p53 protein. Sequencing of the p53 gene in these 9 cases revealed a mutation in only one of these cases, a G-to-A substitution in codon 285 (exon 8). Somewhat unexpectedly, no mutations were identified in PTEN, a commonly altered tumor suppressor gene in de novo glioblastoma multiformes. Unlike some radiation-induced tumors, no activating point mutations of the K-ras proto-oncogene or base pair deletions of tumor suppressor genes were noted. These radiation-induced tumors are distinctive in their high histological grade at clinical presentation. The spectrum of molecular genetic alterations appears to be similar to that described in spontaneous high grade astrocytomas, especially those of the de novo type.

c-myc oncogene family expression in glioblastoma and survival

BACKGROUND

In gliomas, c-myc proto-oncogene expression has been found to correlate with the grade of malignancy, with low expression in Grade I and II and high expression in Grade III and IV tumors. We aimed to discover if myc expression is of prognostic significance in glioblastomas.

METHODS

Expression of the c-myc, N-myc, and L-myc proto-oncogenes and of the max gene was investigated in 46 supratentorial glioblastomas from adult patients using in situ hybridization.

RESULTS

Seventy-eight percent of the tumors expressed c-myc m-RNA, 84% max m-RNA, 57% N-myc m-RNA, and 57% L-myc m-RNA. The postoperative survival of patients over 60 years of age and that of patients under 60 years of age were analyzed separately, since advancing age was found to be negatively correlated with the duration of postoperative survival (p = 0.004). There was no significant difference in postoperative survival in either age group between patients whose tumors expressed either c-myc, N-myc, or L-myc, respectively, and those whose tumors did not exhibit this characteristic. A difference in postoperative survival, however, was found in the over 60-year age group between patients whose tumors expressed max to an equal or lesser extent than c-myc and those whose tumors expressed max to a greater extent than c-myc or neither max nor c-myc.

CONCLUSION

The biologic behavior of glioblastomas in older patients may depend on the relative, but not on the absolute content of the c-myc protein and interacting proteins.

Mutational analysis of the PTEN gene in gliomas: molecular and pathological correlations

The PTEN gene, recently identified on chromosome 10q23, has been proposed to be a candidate tumor suppressor gene inactivated in multiple cancers including glial tumors. We investigated 47 glioblastomas (GBM), 14 anaplastic astrocytomas (AA), 6 non-pilocytic low-grade astrocytomas (LGA), 21 low-grade and anaplastic oligodendrogliomas (O) and oligoastrocytomas (OA), and 3 ependymomas (E) for mutation of the PTEN gene using denaturing gradient gel electrophoresis (DGGE) followed by DNA sequencing. These tumors have been previously screened for loss of heterozygosity (LOH) on chromosome 10q, p53 mutations and EGFR amplification. Overall, PTEN mutations, detected in 14 of 91 tumors, were present in 13 of 47 GBM and 1 of 14 AA. In contrast, mutations were absent in other glioma subtypes (0/30). In all informative cases, PTEN mutations occurred in tumors showing LOH on chromosome 10q, confirming the inactivation of this gene by a 2-hit mechanism. No correlation was observed between the presence of PTEN mutation and p53 mutation and EGFR amplification. Our results indicate that biallelic PTEN inactivation plays an important role in the pathogenesis of high-grade astrocytomas as a late event. Moreover, they suggest that PTEN alterations are equally involved in the 2 glioblastoma pathways defined by the presence of EGFR amplification and p53 mutation. Finally, correlation analysis with clinical data did not show that PTEN mutation was linked to survival of the patients.

Cerebral neoplasms in adults

MRI plays a critical role in the diagnosis, management, and follow-up of adult supratentorial neoplasms. However, there is considerable overlap in the imaging findings of these lesions. New imaging methods, such as functional MRI, diffusion imaging, and spectroscopy may further improve diagnostic specificity and surgical management. Knowledge of the pathogenesis of these tumors, imaging characteristics, and available novel imaging tools will aid the radiologist in making meaningful contributions in the evaluation and treatment of these lesions.

Age-dependent rate of anaplastic transformation in low-grade astrocytoma

Age and histologic grade are interrelated characteristics of diffuse fibrillary astrocytomas, because the peak age incidence rises with increasing grade. The relationship between age and grade may be explained if age determines the rate of anaplastic progression in astrocytomas. The authors tested this hypothesis by determining the interval between diagnosis of low-grade astrocytoma and progression to high-grade astrocytoma in patients of various ages. A two-way scatterplot of age at initial diagnosis versus interval to anaplastic progression demonstrated a strong negative correlation (n = 24; Pearson correlation coefficient = -0.83; Spearman correlation coefficient = -0.79; p < 0.001 for both values). It was concluded that the rate of anaplastic progression in low-grade astrocytoma is directly correlated with patient age.

Comparative molecular genetic profiles of anaplastic astrocytomas/glioblastomas multiforme and their subsequent recurrences

Malignant glial tumors (anaplastic astrocytomas and glioblastomas multiforme) arise mostly either from the progression of low grade precursor lesions or rapidly in a de novo fashion and contain distinct genetic alterations. There is, however, a third subset of malignant gliomas in which genetic lesions remain to be identified. Following surgical resection, all gliomas appear to have an inherent tendency to recur. Comparative molecular analysis of ten primary malignant gliomas (three anaplastic astrocytomas and seven glioblastomas multiforme) with their recurrences identified two distinct subgroups of recurrent tumors. In one group, primary tumors harbored genetic aberrations frequently associated with linear progression or de novo formation pathways of glial tumorigenesis and maintained their genetic profiles upon recurrence. In the other subset with no detectable known genetic mutations at first presentation, the recurrent tumors sustained specific abnormalities associated with pathways of linear progression or de novo formation. These included loss of genes on chromosomes 17 and 10, mutations in the p53 gene, homozygous deletion of the DMBTA1 and p16 and/ or p15 genes and amplification and/or overexpression of CDK4 and alpha form of the PDGF receptor. Recurrent tumors from both groups also displayed an abnormal expression profile of the metalloproteinase, gel A, and its inhibitor, TIMP-2, consistent with their highly invasive behavior. Delineation of the molecular differences between malignant glioblastomas and their subsequent recurrences may have important implications for the development of rational clinical approaches for this neoplasm that remains refractory to existing therapeutic modalities.

p53 protein expression in grade II astrocytomas: immunohistochemical study of 100 cases with long-term follow-up

p53 protein expression was evaluated by immunohistochemistry in a homogeneous series of 100 supratentorial grade II astrocytomas with long-term follow-up. The staining was positive in 72 cases. The proportion of p53 positive tumors was slightly higher in younger patients. The tumor regrowths which derived from p53 positive tumors were themselves p53 positive, and this p53 immunopositivity was often stronger than in the initial tumors. All of the 10 gemistocytic astrocytomas included in our series were p53 positive, and age more than histological type appeared decisive in prognosis. p53 protein expression did not quite reach statistical significance as an independent predictive variable in multivariate analysis, whereas survival was related with age, mass effect, surgery and tumor location. Only a tendency to a longer survival was observed on the curves in younger patients with mildly positive tumors.

A constitutively active epidermal growth factor receptor cooperates with disruption of G1 cell-cycle arrest pathways to induce glioma-like lesions in mice

The epidermal growth factor receptor (EGFR) gene is amplified or mutated in 30%-50% of human gliobastoma multiforme (GBM). These mutations are associated usually with deletions of the INK4a-ARF locus, which encodes two gene products (p16(INK4a) and p19(ARF)) involved in cell-cycle arrest and apoptosis. We have investigated the role of EGFR mutation in gliomagenesis, using avian retroviral vectors to transfer a mutant EGFR gene to glial precursors and astrocytes in transgenic mice expressing tv-a, a gene encoding the retrovirus receptor. TVA, under control of brain cell type-specific promoters. We demonstrate that expression of a constitutively active, mutant form of EGFR in cells in the glial lineage can induce lesions with many similarities to human gliomas. These lesions occur more frequently with gene transfer to mice expressing tv-a from the progenitor-specific nestin promoter than to mice expressing tv-a from the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter, suggesting that tumors arise more efficiently from immature cells in the glial lineage. Furthermore, EGFR-induced gliomagenesis appears to require additional mutations in genes encoding proteins involved in cell-cycle arrest pathways. We have produced these combinations by simultaneously infecting tv-a transgenic mice with vectors carrying cdk4 and EGFR or by infecting tv-a transgenic mice bearing a disrupted INK4a-ARF locus with the EGFR-carrying vector alone. Moreover, EGFR-induced gliomagenesis does not occur in conjunction with p53 deficiency, unless the mice are also infected with a vector carrying cdk4. The gliomagenic combinations of genetic lesions required in mice are similar to those found in human gliomas.

Effects of growth factors and basement membrane proteins on the phenotype of U-373 MG glioblastoma cells as determined by the expression of intermediate filament proteins

Various growth factors and basement membrane proteins have been implicated in the pathobiology of astrocytomas. The goal of this study was to determine the relative contribution of these two factors in modulating the phenotype of U-373 MG glioblastoma cells as determined by the expression of the intermediate filament proteins glial fibrillary acidic protein, vimentin, and nestin. For these determinations, cells plated in serum-free medium were treated either with growth factors binding to tyrosine kinase receptors including transforming growth factor-alpha, epidermal growth factor, platelet-derived growth factor-AA, basic fibroblast growth factor, and insulin-like growth factor-1 or with basement membrane proteins including collagen IV, laminin, and fibronectin. The changes in the expression levels of intermediate filament proteins in response to these treatments were analyzed by quantitation of immunoblots. The results demonstrate that collagen IV and growth factors binding to tyrosine kinase receptors decrease the glial fibrillary acidic protein content of U-373 MG cells. Growth factors binding to tyrosine kinase receptors also decrease the vimentin content of these cells but do not affect their nestin content. On the other hand, basement membrane proteins decrease the nestin content of U-373 MG cells but do not affect their vimentin content. The significance of these results with respect to the role played by different factors in modulating the phenotype of neoplastic astrocytes during tumor progression is discussed.

Microsatellite instability and mutation of DNA mismatch repair genes in gliomas

Microsatellite instability (MSI) has been identified in various human cancers, particularly those associated with the hereditary nonpolyposis colorectal cancer syndrome. Although gliomas have been reported in a few hereditary nonpolyposis colorectal cancer syndrome kindred, data on the incidence of MSI in gliomas are conflicting, and the nature of the mismatch repair (MMR) defect is not known. We established the incidence of MSI and the underlying MMR gene mutation in 22 patients ages 45 years or less with sporadic high-grade gliomas (17 glioblastomas, 3 anaplastic astrocytomas, and 2 mixed gliomas, grade III). Using five microsatellite loci, four patients (18%) had high level MSI, with at least 40% unstable loci. Germline MMR gene mutation was detected in all four patients, with inactivation of the second allele of the corresponding MMR gene or loss of protein expression in the tumor tissue. Frameshift mutation in the mononucleotide tract of insulin-like growth factor type II receptor was found in one high-level MSI glioma, but none was found in the transforming growth factor beta type II receptor and the Bax genes. There was no family history of cancer in three of the patients, and although one patient did have a family history of colorectal carcinoma, the case did not satisfy the Amsterdam criteria for hereditary nonpolyposis colorectal cancer syndrome. Three patients developed metachronous colorectal adenocarcinomas, fitting the criteria of Turcot's syndrome. Thus, MSI and germline MMR gene mutation is present in a subset of young glioma patients, and these patients and their family members are at risk of developing other hereditary nonpolyposis colorectal cancer syndrome-related tumors, in particular colorectal carcinomas. These results have important implications in the genetic testing and management of young patients with glioma and their families.

Long-term survival in a patient with supratentorial glioblastoma: clinical considerations

Glioblastoma, a malignant tumor of neuroepithelial origin, is relatively uncommon in childhood, during which it accounts for 7%-9% of brain tumors. A few patients (about 3%) live more than 5 years. We report a 13-year-old girl who was admitted because one month earlier she had begun to present headache and diplopia. Brain computed tomography (CT) showed a right frontal tumor. At operation, complete excision of the visible tumor was performed. Histologic examination showed that the tumor was a glioblastoma multiforme. The patient underwent 52 Gy of external beam radiotherapy to the enhancing tumor mass plus 3-cm border, and chemotherapy with nitrosourea (BCNU). Fourteen years, 9 months later, the patient presents neither neurological deficits nor radiological relapse. We confirm that younger age, the one immutable prognostic factor, supports a particularly aggressive approach to the treatment of glioblastomas.

Gliosarcoma: an immunohistochemical, ultrastructural and fluorescence in situ hybridization study

Three cases of primary gliosarcoma (GS) were studied by immunohistochemical, ultrastructural and fluorescence in situ hybridization (FISH) methods. All tumors occurred in the supratentorial regions of the body. No patient had a prior history of irradiation to the brain. All patients died of tumor within 1 year, and autopsies were performed in two cases. Microscopically, each of the three tumors showed a mixture of glioblastoma (GBM) and a sarcomatous component (SC), which resembled fibrosarcoma with various histological features. Numerous collagen and reticulin fibers were seen in the SC of all tumors. Glial fibrillary acidic protein (GFAP) was immunoreactive only in the gliomatous component (GC). Factor VIII-related antigen was negative except for endothelial cells. One tumor exhibited alpha-smooth muscle actin positivity in the SC. Expression of MIB-1 and p53 protein was demonstrated in both components for all tumors. Labeling indices (LI) for MIB-1 ranged from 7.7 to 36.1%, and LI for p53 protein ranged from 2.9 to 57.0%. Ultrastructurally, astrocytic cells were characterized by a polygonal configuration with many cytoplasmic projections and occasional filaments. Spindle-shaped fibroblasts in the SC contained well-developed rough endoplasmic reticulum. Fluorescence in situ hybridization (FISH) performed on fresh materials or paraffin-embedded tissue demonstrated single signals for chromosome 10 in 40.6-58.3% of cells and for chromosome 17 in 37.9-48.6% of cells. Two tumors were regarded as containing losses of both chromosomes 10 and 17, while the third showed a substantial loss only of chromosome 10. As similar aberrations have been reported in GBM, these chromosomal abnormalities suggest a common pathogenesis in GS and GBM.

Cell adhesion molecule Nr-CAM is over-expressed in human brain tumors

Using the technique of differential display-polymerase chain reaction (DD-PCR), we isolated a cDNA fragment that is over-expressed in glioblastoma multiforme tissue as compared to normal brain tissue. Sequence analysis indicated that this sequence is identical to the previously isolated human neuron-glia-related cell adhesion molecule hNr-CAM. Gene-specific RT-PCR analysis indicated that hNr-CAM is over-expressed in high-grade astrocytomas, gliomas and glioblastoma tumor tissues as compared to normal brain tissue. High levels of hNr-CAM expression also were observed in cell lines derived from astrocytomas, gliomas and glioblastoma multiforme tumors. Low levels of hNr-CAM expression were observed in neuroblastoma, meningiomas, melanoma, normal breast and prostate tumor tissues. Northern blot analysis showed an alternatively spliced mRNA of 1.4 kb in several tumors as compared to the 7.5 kb transcript found in normal brain tissue. Genomic Southern blot analysis of DNA from 3 brain tumor cell lines showed that over-expression of hNr-CAM in brain tumors was not due to gene amplification. In situ hybridization analysis indicated that 11 of the 20 human brain tumor samples studied showed hNr-CAM over-expression. Our results suggest that hNr-CAM is over-expressed in malignant brain tumors and can serve as a novel marker for brain tumor detection and perhaps therapy.

Telomerase activity in human gliomas

OBJECTIVE

Telomerase activity, which is undetectable in most mature normal tissues, has been identified in many types of human cancers, including neuroblastomas and oligodendrogliomas. These findings suggest that a novel mechanism in addition to activation of oncogenes and inactivation of tumor suppressor genes may play an important role in tumorigenesis. The goal of the present study was to assess and correlate the telomerase activity in astrocytic gliomas of different grades.

METHODS

Telomere repeat amplification protocol and Southern blot hybridization with telomere-specific probes were used to detect telomerase activity and to measure terminal restriction fragment length, respectively.

RESULTS

Telomerase activity was detected in 3 of 9 (33%) low-grade astrocytomas (World Health Organization Grade II), 5 of 11 (45%) anaplastic astrocytomas (World Health Organization Grade III), 36 of 41 (89%) glioblastomas multiforme (World Health Organization Grade IV), 3 of 4 (75%) oligodendrogliomas, and none of 4 normal brain specimens.

CONCLUSION

We demonstrated that telomerase activity is absent in normal brain tissues while present in most glioma samples (72%). The frequency of such activity increases with malignancy. These results suggest that telomerase activity may be used as a tumor marker and that the activation of telomerase may correlate with initiation and malignant progression of astrocytic tumors.

The molecular genetics of central nervous system tumors

Over the past few years, although much has been learned about the molecular genetics of central nervous system (CNS) tumors, researchers and pathologists are only beginning to understand the scientific basis of the development of these tumors. Data accumulated so far support the division of glioblastoma into two clinical and molecular subsets. Primary or de novo glioblastomas occur in older patients, are clinically aggressive and exhibit epidermal growth factor receptor amplification or overexpression. Secondary glioblastomas develop from pre-existing low-grade astrocytomas, have a more protracted clinical course, and frequently contain p53 mutations. Both types of tumors show deletions of chromosome 10 and possibly mutations of the PTEN/MMAC1 gene as an endstage event. Oligodendrogliomas have been shown to have genetic abnormalities distinct from those of the astrocytic tumors, commonly involving chromosomes 1p and 19q. As regards meningiomas, loss of chromosome 22q and mutations of the neurofibromatosis type 2 gene are frequent events and loss of chromosome 14q and 10q may be seen in atypical or malignant transformation. Such genetic findings, apart from providing a better understanding of neoplastic transformation in brain tumors, are beginning to form the basis of a new approach to neuro-oncology.

Genetic sub-types of human malignant astrocytoma correlate with survival

In human malignant astrocytoma, age of the patient and histological grade of the tumor are important prognostic variables. Several genetic changes have been reported to occur in these tumors, which may be of additional and independent prognostic relevance. To determine their prognostic significance, we analyzed 75 high-grade tumors, 12 anaplastic astrocytomas and 63 glioblastomas multiforme, for the presence of genetic changes that occur frequently in high-grade astrocytoma, i.e., loss of heterozygosity (LOH) for chromosome 10, p53-gene alteration (mutation and/or LOH), and EGFR-gene amplification. We defined 4 groups of patients who showed a specific combination of genetic changes in the tumor: group 1, p53-gene alteration without complete LOH 10; group 2, complete LOH 10 only; group 3, p53-gene alteration + complete LOH 10; group 4, complete LOH 10 + EGFR-gene amplification. In univariate analysis, the log-rank test revealed significant differences in survival between patients of group 1 (median survival of 13 months) and group 3 (median survival of 5.2 months, p = 0.0058) and between patients of group 1 and group 4 (median survival of 4 months, p = 0.0033). In multivariate analysis, age and genetic sub-type proved to be important prognostic variables, whereas histological grading was less important. The age-corrected survival time for group-4 patients is significantly shorter than that for group-1 patients (relative risk = 3.79, p = 0.0075). Our data indicate that genetic sub-type is an important prognostic variable in human high-grade astrocytoma.

Investigation of genetic alterations associated with the grade of astrocytic tumor by comparative genomic hybridization

Comparative genomic hybridization (CGH) is a technique that allows the detection of losses and gains in DNA copy number across the entire genome. We used CGH to study the genetic alterations that occur in primary astrocytomas, including 14 glioblastomas (GBM), 12 anaplastic astrocytomas (AA), and 7 low-grade astrocytomas (LGA). The average numbers of total aberrations in GBM, AA, and LGA were 9.7, 5.4, and 4.0, respectively. The average number of DNA sequence losses in GBM was significantly higher than that in AA or LGA (P < 0.01). Frequently altered regions (> eight cases) observed in all grades of astrocytoma were 7p13-p12 (gain), 7q31 (gain), 8q24.1-q24.2 (gain), 9p21 (loss), 10p12-p11 (loss), 10q22-qter (loss), 13q21-q22 (loss), and 20q13.1-q13.2 (gain). Loss of 9p, 10p, or 10q, and the gain or amplification of 7p, were observed frequently in GBM (64%, 57%, 64%, and 50% of cases, respectively). Frequent alterations found in AA were losses of 9p, 10q, and 13q, and gains of 1q, chromosome 7, 11q, and Xq. Whereas 7p13-p11 amplification occurred exclusively in cases with the loss of all or part of chromosome 10, this change never occurred in cases having an increase in copy number of 8q, which was the most frequent change observed in LGA (four of seven cases). These results may indicate that an increase in copy number of 8q is an important event in GBM, with a genetic pathway, which is distinct from that in GBM with 7p amplification.

Long-term survival in patients with supratentorial glioblastoma

The authors report 11 patients with cerebral glioblastoma who lived at least 5 years after their initial diagnosis. There were 6 female and 5 male; the mean age was 39 years (range 24-55 years). All patients were treated surgically and postoperatively received whole-brain radiotherapy and chemotherapy. Five patients (45%) presented local recurrences after an average interval of 3.9 years from treatment. At average follow-up of 9 years (range 5-14 years), 7 patients (64%) were alive after an average interval of 8.1 years; 4 patients (36%) died from local relapse. Survival was influenced by patient age and, to a lesser degree, by treatment. A review of the literature, together with our own series, suggest that death from recurrence disease is unusual in glioblastoma patients who survive more than 5 years.

Gliomas in families: chromosomal analysis by comparative genomic hybridization

Gliomas that aggregate in otherwise unremarkable families may have a heritable genetic basis. To determine the spectrum of genetic alterations in glioma-susceptible families, we examined tumor DNA from familial cases for regions of chromosomal gain or loss using comparative genomic hybridization (CGH). We compared chromosomal alterations within and among glioma families to those found in sporadic gliomas. A specific chromosomal abnormality common to the tumors of multiple unrelated probands with glioma or a specific chromosomal abnormality common to multiple affected persons in a single glioma-prone family would support the hypothesis of an inherited predisposition to glioma and at the same time identify specific regions of the genome harboring putative glioma susceptibility genes. Tumor DNA from 11 patients from seven families with two or more individuals with glioma was analyzed, including three members of a remarkable family having 10 affected individuals. We found no chromosomal abnormality common to all tumors of all probands nor did we find family-specific abnormalities in two of three glioma-prone kindreds. There were frequent copy number aberrations (CNAs) on chromosomes 7, 10, 19, and the sex chromosomes; other CNAs included +3q(13.3-29), -4q, +5q, -9q34, +12, -13q(21-->33), -15, -16p, +17qter, -18, -21, and -22. Amplifications occurred at +2 7p(11.1-->12), +2 7q(21.2-->33), +2 12q(13.2-->14), and +2 12p(11-->12). Although there were several novel CNAs [-16p, and +2 12p(11-p12)], none could readily explain the inheritance of these tumors.

Functional GABA(A) receptors on human glioma cells

Glioma cells in acute slices and in primary culture, and glioma-derived human cell lines were screened for the presence of functional GABA(A) receptors. Currents were measured in whole-cell voltage clamp in response to gamma-aminobutyric acid (GABA). While cells from the most malignant glioma, the glioblastoma multiforme, did not respond to GABA, an inward current (under our experimental conditions with high Cl- concentration in the pipette) was induced in gliomas of lower grades, namely in 71% of oligodendroglioma cells and in 62% of the astrocytoma cells. Glioma cell lines did not express functional GABA(A) receptors, irrespective of the malignancy of the tumour they originate from. The currents elicited by application of GABA were due to activation of GABA(A) receptors; the specific agonist muscimol mimicked the response, the antagonists bicuculline and picrotoxin blocked the GABA-activated current and the benzodiazepine receptor agonist flunitrazepam augmented the GABA-induced current and the benzodiazepine inverse agonist DMCM decreased the GABA current. Cells were heterogeneous with respect to the direction of the current flow as tested in gramicidin perforated patches: in some cells GABA hyperpolarized the membrane, while in the majority it triggered a depolarization. Moreover, GABA triggered an increase in [Ca2+]i in the majority of the tumour cells due to the activation of Ca2+ channels. Our results suggest a link between the expression of GABA receptors and the growth of glioma cells as the disappearance of functional GABA(A) receptors parallels unlimited growth typical for malignant tumours and immortal cell lines.

Genomic changes in glioblastoma cell lines detected by comparative genomic hybridization

Comparative genomic hybridization serves as a screening test for regions of copy number changes in tumor genomes. We have applied the technique to map DNA gains and losses in 5 cell lines derived from glioblastoma multiforme, the most common primary neoplasm of the central nervous system. The most frequent losses occurred on chromosomes 10 and 13. The most common gains were observed on chromosomes 5, 6, 7 and 20. Some novel sites of genomic alterations were also observed. Analysis of common areas of loss and gain in these cell lines provides a basis for future attempts to more finely map these genetic changes and for elucidation of genes involved in tumor progression.

Molecular neuropathology of astrocytic brain tumors

Both surgical and molecular neuropathologists have recently achieved remarkable progress in the histogenetic classification and molecular characterization of human gliomas. Major histopathological achievements in the revised WHO classification include the introduction of immunohistochemical reagents for glial fibrillary acidic protein and for the proliferation-associated antigens, the definition of glioblastoma multiforme as an astrocytic neoplasm and the recognition of the pleomorphic xantho--astrocytomas as a novel clinico-pathological entity. In molecular neuropathology, alterations of oncogenes and tumor suppressor genes and their potential functions have been identified, microsatellite analyses have revealed novel loci for putative tumor suppressor genes and distinct molecular pathways for different tumor entities are beginning to emerge. Mutations in cell cycle regulatory genes are present in most glioblastomas and may account for their striking growth potential. Autocrine and paracrine growth factors and their respective protein tyrosine kinase receptors appear to contribute both to glial and endothelial cell proliferation. In our contribution, we would like to focus on astrocytic gliomas. Findings with potential diagnostic relevance include changes associated with malignant progression of low grade astrocytomas, patterns of genetic alterations which allow to further differentiate histopathological entities such as the glioblastoma multiforme into genetically distinct subsets and mechanisms of tumor angiogenesis in malignant gliomas. One of the major tasks ahead is to establish correlations and relationships between histopathological, molecular and clinical data. This will require a long-term collaboration between molecular neuropathologists, neurosurgeons and clinical neuro-oncologists.

Neuropathology of pediatric brain tumors

Pediatric central nervous system neoplasms include a spectrum of both glial and nonglial tumors that differ significantly in location and biological behavior from those of adults. Brain tumors in infants and children most often arise from central neuroepithelial tissue, whereas a significant number of adult tumors arise from central nervous system coverings (e.g., meningioma), adjacent tissue (e.g., pituitary adenoma), or metastases. Most adult brain tumors are supratentorial malignant gliomas, whereas the most common malignant pediatric brain tumor is the cerebellar primitive neuroectodermal tumor (medulloblastoma). This article reviews neuropathological characteristics of the more common pediatric brain tumors. Entities, such as the brainstem glioma, and less common neoplasms like the desmoplastic infantile ganglioglioma and the central nervous system atypical teratoid/rhabdoid tumor are reviewed because they occur almost exclusively in children. Known cytogenetic and molecular characteristics of childhood brain tumors are also reviewed.

Elevated levels of mortalin expression in human brain tumors

We have performed immunohistochemical studies of mortalin in normal and tumor human brain sections. In normal brain sections, the expression was seen mainly as being confined to neurons. Normal astrocytes showed undetectable expression of this unique member of the heat shock 70 protein family. Three grades of astrocyte tumors (low-grade astrocytoma, anaplastic astrocytoma, and glioblastoma), however, showed an increasing number of mortalin-positive cells. Other types of brain tumors, such as meningiomas, neurinomas, pituitary adenomas, and metastases, also showed elevated levels of mortalin expression compared to those in the normal brain. Mortalin has earlier been reported to have differential intracellular distribution in normal and transformed cells in vitro. Therefore, we substantiated the present study with immunofluorescence localization of the protein in normal and glioblastoma cells. The observations indicated that the tumors might be expressing a nonpancytosolic mortalin. An increase in number of mortalin-positive cells with malignant progression of brain tumors and its correlation with Ki-67 (a cell proliferation marker)-positive cells further suggested an involvement of nonpancytosolic mortalin(s) in malignant transformation of cells in vivo.

Analyses of human gliomas by restriction landmark genomic scanning

The 16 primary gliomas were examined for changes in genomic DNA using a recently developed 2-dimensional gel electrophoresis method called restriction landmark genomic scanning (RLGS). This approach allows detection of DNA amplification, deletion, methylation and potentially other genetic rearrangements represented as decreases and increases in spot/fragment intensity on an autoradiogram. Approximately 2,000 landmark sites in tumor DNA were compared with those of DNA isolated from normal brain tissues. Seven spots showing intensified signal were consistently detected in at least 50% of tumors, implying activation of corresponding DNA sequences, and 8 additional spots having reduced signal were observed, again in more than 50% of all tumors, suggesting inactivation by the loss of 1 allele or homozygous deletion. Decreased signal may also infer relative CpG island methylation state. Of those spots consistently identified in tumors, 2 amplified and 4 reduced spots were found to be characteristic of low- and high-grade tumors, while the remaining 5 amplified and 4 reduced spots were associated with high-grade gliomas only, suggesting a link of specific mutations to degree of malignancy. A separate subset of glioblastomas evaluated, however, showed no alterations in these 'hot spots' which were detected in even low grade astrocytomas. The results demonstrate the genetic heterogeneity of glioblastoma and implicate the progression of neoplasia via differing genetic pathways.

Hemizygous or homozygous deletion of the chromosomal region containing the p16INK4a gene is associated with amplification of the EGF receptor gene in glioblastomas

The p16INK4a gene product acts as a negative regulator of the cell cycle by binding to cyclin-dependent kinases (CDKs) 4 and 6, thereby inhibiting the formation of an active CDK/cyclin D complex. Deletion of the p16 locus has been observed in tumor cell lines and, less frequently, in primary human neoplasms. We analyzed 31 glioblastomas and identified 6 cases with hemizygous and 6 with homozygous deletions of the p16 locus. Eight of these cases showed a concurrent amplification of the EGFR gene (epidermal growth factor receptor) while the overall frequency was 35%. This close correlation suggests that deletion of the p16 chromosomal region constitutes another genetic hallmark of the primary glioblastoma, which rapidly develops de novo, without a less malignant precursor lesion and for which EGFR amplification is a characteristic genetic change. The p16 protein was not detectable in 15 of 22 glioblastomas but only 4 of these showed homozygous deletion of the gene. The alternative transcript p16 beta, for which a growth-suppressing function has been suggested, was co-expressed with p16 alpha mRNA in most cases. Hypermethylation of CpG islands in the 5' region of the p16 gene was identified in only 1 case, suggesting that this alternative mechanism of gene silencing is rarely responsible for loss of p16 expression in glioblastomas. Likewise, only 1 glioblastoma carried a p16 mutation and in addition, unexpectedly, a homozygous deletion of p16 in approximately 80% of tumor cells. This mutation, Arg24Pro, has previously been identified in a melanoma kindred.

Molecular aspects of neuro-oncology

Detailed understanding of molecular events responsible for brain tumor growth is a prerequisite for the development of effective therapeutic modalities leading to improved prognosis and cure. Advances in molecular biology in the past decades have revolutionized our understanding of cancer, including brain tumors. We have learned that abnormal proliferation, inability of the cells to die and their potential to modify their tissue environment result from accumulation of genetic aberrations. This article reviews genetic mechanisms implicated in the pathogenesis of nervous system tumors, such as unactivation of tumor suppressor and replication error genes, generation of abnormal growth factor loops, alterations of apoptotic pathways and angiogenesis.

p53 protein in pediatric malignant astrocytomas: a study of 21 patients

Malignant astrocytomas are uncommon brain tumors in children and it is known that astrocytic tumors with similar degrees of histologic anaplasia often show different biologic behaviour. Their uncommon occurrence has resulted in relatively few studies of the molecular biology and genetics of pediatric malignant astrocytomas with somewhat conflicting results, in contrast with the many studies addressing astrocytomas in adults. p53 immunoreactivity has been used to screen tissues for the abnormal presence of the p53 protein and abnormal immunoreactivity has been demonstrated in one-half to two-thirds of adult astrocytomas. We studied the frequency of p53 immunoreactivity and gene alteration in 21 children with malignant astrocytomas (anaplastic astrocytoma and glioblastoma multiforme) and analysed the survival of patients with p53 immunoreactive versus non-reactive tumors. Of the cases examined, 8 were anaplastic astrocytoma (AA) and 13 were glioblastoma multiforme (GM). We found that the overall frequency of p53 immunoreactivity of 47% in this group of pediatric malignant astrocytomas is similar to that reported for adult astrocytomas. The median survival in both p53-positive and p53-negative groups of pediatric malignant astrocytomas was similar: however, the number of deaths in each group and the distribution of p53 scores is not statistically significant. Further studies to precisely identify p53 and other genetic mutations in pediatric gliomas are needed to understand their biology and the rationale for therapeutic options.

A molecular genetic model of astrocytoma histopathology

As the molecular events responsible for astrocytoma formation and progression are being clarified, it is becoming possible to correlate these alterations with the specific histopathological and biological features of astrocytoma, anaplastic astrocytoma and glioblastoma multiforme. In WHO grade II astrocytomas, autocrine stimulation by the plateletderived growth factor system coupled with inactivation of the p53 gene may lead to a growth stimulus in the face of decreased cell death with slow net growth ensuing. Such cells would also have defective responses to DNA damage and impaired DNA repair, setting the stage for future malignant change. Such biological scenarios recapitulate many of the clinicopathological features of WHO grade II astrocytomas. Anaplastic astrocytomas further display release of a critical cell cycle brake that involves the CDKN2/p16, RB and CDK4 genes. This results in mitoses seen histologically; clinically, there is more conspicuous, rapid growth. Finally, glioblastomas may emerge from the microenvironmental outgrowth of more malignant clones in a complex vicious cycle that involves necrosis, hypoxia, growth factor release, angiogenesis and clonal selection; growth signals mediated by activation of epidermal growth factor receptors may precipitate glioblastomas. It is clear as well that glioblastoma multiforme can arise via a number of independent genetic pathways, although the clinical significance of these distinctions remains unclear.

Homozygous p53 gene mutation in a radiation-induced glioblastoma 10 years after treatment for an intracranial germ cell tumor: case report

OBJECTIVE

Radiation-induced glioma is a rare but serious complication of radiotherapy. Underlying radiation-induced mutations in oncogenes or tumor suppressor genes have not previously been described.

CLINICAL PRESENTATION

A 16-year-old female patient developed a glioblastoma in the right frontal lobe 10 years after treatment of a suprasellar germ cell tumor with 50 Gy ionizing radiation. The glioblastoma was undetectable on a high-resolution magnetic resonance image obtained 3 months before diagnosis.

METHODS AND RESULTS

A p53 functional assay was used to examine the transcriptional competence of the p53 tumor suppressor gene. This assay scores the content of mutant p53 alleles in tumor and blood samples quantitatively as a percentage of red yeast colonies. The glioblastoma contained 95% mutant p53 alleles, whereas blood from the patient and her parents contained only normal background levels of red colonies. Sequencing revealed that the mutation in the tumor was a 3-base pair deletion affecting codons 238 and 239. Intragenic deletion within the p53 deoxyribonucleic acid binding domain is uncommon in sporadic tumors but would be entirely consistent with misrepair of a radiation-induced double-strand deoxyribonucleic acid break in this case.

CONCLUSION

This is the first case in which a causative underlying genetic event has been identified in a radiation-induced glioblastoma. We infer that mutation of one p53 allele occurred at the time of radiotherapy, and the sudden appearance of the tumor 10 years later occurred after loss of the remaining wild-type allele and/or other genetic alterations, such as chromosome 10 loss and epidermal growth factor receptor gene amplification.

Hydroxyurea accelerates the loss of epidermal growth factor receptor genes amplified as double-minute chromosomes in human glioblastoma multiforme

OBJECTIVE

We sought to determine whether hydroxyurea could accelerate the loss of amplified epidermal growth factor receptor (EGFR) genes from glioblastoma multiforme (GBM). There is good reason to think that elimination of amplified EGFR genes from GBMs will negatively impact tumor growth. Hydroxyurea has previously been shown to induce the loss of amplified genes from extrachromosomal double minutes (dmin) but not from chromosomal homogeneously staining regions.

METHODS

Pulsed-field gel electrophoresis and Southern blot hybridization were used to demonstrate EGFR genes amplified as dmin. Giemsa-stained metaphase spreads were prepared in an attempt to visualize dmin. A GBM cell line containing amplified EGFR genes was treated continuously in vitro with 0 to 150 mumol/L hydroxyurea, and slot blot analysis was used to show the loss of amplified EGFR genes.

RESULTS

Amplified EGFR genes were found on dmin in 4 of 11 (36%) fresh human GBM biopsy specimens. None of the GBMs contained EGFR genes amplified as homogeneously staining regions. Amplified dmin were not microscopically visible when stained with Giemsa because of their small size. Slot blot analysis showed that these low doses of hydroxyurea accelerated the loss of amplified EGFR genes in a dose- and time-dependent fashion. Pulsed-field gel electrophoresis and Southern blot analysis confirmed that EGFR gene loss was accompanied by amplified dmin loss in a dose-dependent fashion.

CONCLUSION

These studies suggest the potential use of low-dose hydroxyurea in the treatment of GBMs.

Lack of prognostic relevance of alterations in the epidermal growth factor receptor-transforming growth factor-alpha pathway in human astrocytic gliomas

Alterations in the epidermal growth factor receptor (EGFR) and its main ligand, transforming growth factor-alpha (TGF alpha), were investigated for a possible prognostic relevance in 125 astrocytic gliomas (44 World Health Organization (WHO) Grade II, 19 WHO Grade III, and 62 WHO Grade IV tumors). The TGF alpha and EGFR proteins were detected immunohistochemically using monoclonal antibodies. A positive immunoreaction to TGF alpha was detected in 33 (75%) of 44 WHO Grade II astrocytomas, 18 (95%) of 19 WHO Grade III astrocytoma, and 50 (81%) of 62 WHO Grade IV glioblastomas. No correlation between TGF alpha immunoreaction and duration of survival could be found. A positive EGFR immunoreaction was detected in seven (16%) of 44 WHO Grade II astrocytomas, five (26%) of 19 WHO Grade III astrocytomas, and 32 (52%) of 62 WHO Grade IV glioblastomas. Of these gliomas, 97 (26 WHO Grade II, 17 WHO Grade III, and 54 WHO Grade IV gliomas) were examined for EGFR gene amplification using a differential polymerase chain reaction assay. Amplification of the EGFR gene was detected in none of the WHO Grade II astrocytomas, one (6%) of 17 WHO Grade III astrocytomas, and 18 (33%) of 54 WHO Grade IV glioblastomas. Twenty-two of the tumors investigated showed a positive EGFR immunoreaction without detectable gene amplification (five WHO Grade II, four WHO Grade III, and 13 WHO Grade IV tumors). Gene amplification was invariably associated with a positive EGFR immunoreaction. For the entire study group, a strong correlation between EGFR alterations (gene amplification and positive immunoreaction) and survival could be found. However, this correlation only reflected the higher percentages of cases with EGFR alterations in malignant gliomas and was not an independent prognostic factor as determined by multifactorial analysis. These data demonstrate that EGFR alterations are frequent events in astrocytic gliomas and are largely restricted to glioblastomas. However, within one tumor grade they do not provide prognostic information.

Overexpression of the EGF receptor and p53 mutations are mutually exclusive in the evolution of primary and secondary glioblastomas

Glioblastoma multiforme, the most malignant human brain tumor, may develop de novo (primary glioblastoma) or through progression from low-grade or anaplastic astrocytoma (secondary glioblastoma). We present further evidence that primary and secondary glioblastomas constitute distinct disease entities which develop through the acquisition of different genetic alterations. We analyzed p53 mutations, p53 protein accumulation and epidermal growth factor receptor (EGFR) overexpression in 49 biopsies classified as primary or secondary glioblastoma according to clinical and histopathologic criteria. Patients with primary glioblastoma were selected on the basis of a clinical history of less than 3 months and histopathologic features of glioblastoma at the first biopsy (19 cases; mean age, 55 years). The diagnosis of secondary glioblastomas required at least two biopsies and clinical as well as histologic evidence of progression from low grade or anaplastic astrocytoma (30 cases; mean age, 39 years). DNA sequence analysis showed that p53 mutations were rare in primary glioblastomas (11%) while secondary glioblastomas had a high incidence of p53 mutations (67%), of which 90% were already present in the first biopsy. The incidence of p53 protein accumulation (nuclear immunoreactivity to PAb 1801) was also lower in primary (37%) than in secondary glioblastomas (97%). In contrast, immunoreactivity for the EGF receptor prevailed in primary glioblastomas (63%) but was rare in secondary glioblastomas (10%). Only one out of 49 glioblastomas showed EGFR overexpression and a p53 mutation. These data indicate that overexpression of the EGF receptor and mutations of the p53 tumor suppressor gene are mutually exclusive events defining two different genetic pathways in the evolution of glioblastoma as the common phenotypic endpoint.

Molecular biology of pediatric gliomas

The genes involved in the genesis and progression of adult astrocytic tumors have been an area of considerable investigation. The tumor suppressor gene, p53, has been implicated, as has the epidermal growth factor receptor gene. Additional currently unidentified genes lie on chromosomes 10 and 19. Interestingly, work on pediatric astrocytomas suggests that the genes involved are different. p53 is rarely mutated in pediatric tumors, the epidermal growth factor receptor gene is rarely amplified or mutated, and chromosome 10 deletions are rare. The only pediatric tumor that seems to mimic the findings in adult tumors is brainstem glioma, perhaps explaining the uniformly grim prognosis in this type of tumor. In the pilocytic astrocytoma of childhood, mutations in the neurofibromatosis type I gene have been implicated in tumor development. In this review, the oncogenesis of pediatric gliomas is discussed and compared and contrasted to what is known about tumors.

Multiple infusions of anti-epidermal growth factor receptor (EGFR) monoclonal antibody (EMD 55,900) in patients with recurrent malignant gliomas

In a prospective phase I/II trial, EMD 55,900, a murine monoclonal antibody (MAb) directed against EGF receptor, was administered at tumour recurrence to 16 patients previously treated with surgery, radiotherapy and chemotherapy for high grade supratentorial gliomas (11 glioblastomas, five anaplastic astrocytomas). Duration of treatment was planned for at least 4 weeks. The first 10 patients received 40 mg of MAb three times per week (median cumulative dose, 760 mg) and the last 6 patients received 200 mg three times per week (median cumulative dose, 2400 mg). Serum levels of EMD 55,900 were proportional to the injected dose. Repeated infusions of EMD 55,900 were well tolerated. In 13/16 patients, there were no adverse events. Among the 3 others, one had a grade IV neutropenia, one had a clinically asymptomatic hepatitis, and one had a skin rash. This last patient was the only one who had increased human antimouse antibodies (HAMA). After 4 weeks of therapy, 13 patients were evaluable for response. No measurable tumour regression was obtained with either schedule. 6 of the 13 patients (46%) showed evidence of progressive disease, while 7/13 (54%) had stable disease. All patients had progressive disease by 3 months. In this study, repeated infusions of EMD 55,900 were well tolerated but no therapeutic benefit was demonstrated.

Bromodeoxyuridine labeling index in glioblastoma multiforme: relation to radiation response, age, and survival

PURPOSE

Various measures of the rate of tumor cell proliferation have been found to predict survival in patients with intracerebral gliomas. We correlated the bromodeoxyuridine labeling index (BrdUrd LI) with the response to radiation therapy, survival, and known prognostic factors in a series of patients with glioblastoma multiforme (GM) to test its utility as a prognostic factor.

METHODS AND MATERIALS

The BrdUrd LI was determined in 200 newly diagnosed intracranial GMs. Age and sex were known for all patients. The response to radiation therapy was determined in 116 patients by comparing neuroimaging studies obtained before and after external beam radiation therapy. Survival was analyzed in 64 patients who were treated according to two consecutive prospective clinical protocols.

RESULTS

The median BrdUrd LI was 6.5% (mean, 7.2%; range, 1.1-25.4%). The BrdUrd LI did not correlate significantly with age, sex, radiation response, or survival. Age and Karnofsky performance score were independent prognostic factors in our cohort.

CONCLUSION

The proliferative rate as measured by BrdUrd LI was not a prognostic factor in our GM cohort. The BrdUrd LI did not correlate significantly with known prognostic factors in GM. There was no significant relationship between BrdUrd LI and radiation response.